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Mouse Trap Indicator

I've been thinking for a while about how to make a mouse trap that turns ON an LED after it's set off. The reason being for all of us who have a couple traps in the basement or garage that you don't necessarily check everyday. I wanted something that would get my attention that I caught a mouse without having to go right up to it. I also wanted to do that as simple as possible (ie no arduino to post a tweet). Here's what I came up with.

Step 1: Materials & Tools

One of the biggest things I wanted was to make sure I used Items I already had around and were fairly common. The only exception was I did buy some mini-clothes pins instead of using a regular size one because I liked the compactness of it. And I could mount it on top. But you can use a regular one and either attach it to the bottom of the mousetrap, or the side.

- An LED
- Duct tape
- wire
- 3V battery & case (I pulled this one off an old motherboard)
- clothes pin (you can get these as most major craft stores)
- mouse trap

Tools:

- Soldering iron
- glue gun
- wire cutters
- helping hands are a plus

Step 2: Pull Tab

Cut a piece of duct tape and fold it over the action bar. I later trimmed it to about 1cm wide on the left side. That way it doesn't interfere with the trigger bar in the middle.

As a side benefit, it also acts as a pull tab so you don't have to touch the mouse when releasing it from the trap.

Step 3: Prep the Switch

Strip about 2in off the ends of each wire and wrap them around each of the jaws of the clothes pin. I found starting the wrap with my needle-nose pliers really helped.

The closed position with obviously be on. While set we'll be putting that strip of duct tape in between it to stop the current.

Step 4: Solder It All Together

This is basically connecting the battery to the LED through the clothes pin. Again, keeping the the theme of being as simple as possible. Connect one of the wires from the clothes pin to the positive terminal of the battery case and the other wire to the positive leg of the LED. Then connect the negative leg of the LED to the negative of the battery case. If you put your battery in now it should light up.

Step 5: Glue It On

Here I simply used my hot-glue gun and glued it to the top of the mouse trap. I wanted to use my Gorilla glue for a more secure hold, but it was dried out. And this seemed hold better than I thought. After several tests runs it was still holding great.

I faced the LED out the back rather than pointed up because these mousetraps tend to flip when sprung and I wanted to make sure it was visible no matter which side it landed on.

Step 6: You're Done!

Now just put the strip of duct tape in between the jaws of the clothes pin when setting the trap. When the trap springs, the strip will be pulled out, setting the connection and the LED will turn on. That's it. Easy enough right?

Of course the builder in me wants to take it to the next level. One idea I had was to make the LED blink so you're more likely to notice it. The other is to add a joule thief to the circuit so you can run it off 1 AA battery that's close to dead. But there are plenty of great instructables on those you can find.

Perhaps the little music playing circuit from a musical birthday card would be the best thing for that. A bit morbid maybe but the batteries last ages and they come with a simple sprung steel switch. They come with all sorts of songs and there are a few where you can record your own. (I'm sure there must be one out there with Chopin's Funeral March for sale somewhere)

I've thought about this same problem, especially for traps in my roof crawlspace where I don't want to go looking unless I know I've caught a rat. What I think would work pretty well is a little 500kHz oscillator, feeding a little antenna, that's gated on/off by some logic at say 1Hz. Then you could tune to the bottom of an AM radio dial, listening for a gated unmodulated carrier. Radio hiss would turn on and off at the gate clock when the trap is sprung.

The LED idea is of course simpler and works fine if you can see, though I'd stick a resistor to cut the LED current way down for max battery life. Since you'll likely be looking at traps in the dark, even 1mA of LED current should be easy to spot.

I thought about that too. But then I realized I'm most likely to catch mice at night when they're out and about. And I'd like to avoid the chance I'd be woken up for that, even though there would be that little bit of gratification knowing it worked.

But I'm a light sleeper. Plus I have a 1yr old. So I really wasn't risking waking him up either. I'm sure you could make it quiet enough that you'd only hear it if you were in the same room. So good idea.

for those of us without a need to sleep or small children, you could take one of those speaker things from out of a musical greeting card and wire it up to a repeating circuit. also, the speaker thing has a switch like the one you made already on it, so you could just use the unit on its own. the only problem is that the songs in musical greeting cards are fantastically annoying. by the way, great project. to take it to yet another level, you could make it so that the trap would send out a radio signal to a central control board, which would light an LED to notify. that way you could have a bunch of traps used at once and know which ones you had to go empty.